A drug that stimulates the PARASYMPATHETIC NERVOUS SYSTEM. The actions of such drugs resemble those of ACETYLCHOLINE. Those cholinergic actions include stimulation of musculoskeletal muscle, reduction in the heart rate, greater tension in involuntary (or smooth) muscle, increasing glandular secretions such as saliva, and constriction of the pupil of the EYE. MYASTHENIA GRAVIS, GLAUCOMA, certain disorders of the cardiovascular system, and intestinal or bladder malfunction are among the conditions for which cholinergic drugs are prescribed.